This invention relates to water treatment and particularly to the treatment of swimming pool water.
Swimming pool water is usually maintained clean and free of bacteria, fungi and algae by means of chlorination. A typical chlorination reagent is calcium hypochlorite. However the bacteria, fungi and algae become resistant to a consistent level of chlorination over a period of time and it is therefore necessary to treat the water periodically with an agent which is capable of dealing with the resistant bacteria, fungi and algae. Such an agent is known as a super-chlorination or back-up agent.
In the specification of South African Pat. No. 73/9529, the contents of which are incorporated herein by reference, there is described a method of treating water for controlling the growth of bacteria and algae in which a suitable quantity of a linear polymeric biguanide or a salt thereof which in its free base form has a recurring polymer unit represented by the formula ##STR2## wherein X and Y represent bridging groups in which together the total number of carbon atoms directly interposed between the pairs of nitrogen atoms linked by X and Y is more than 9 and less than 17. A preferred polymeric biguanide is poly(hexamethylene biguanide) hydrochloride sold under the trade name Baquacil SB by Imperial Chemicals Industries Limited. This water treatment method has the advantage that it is completely chlorine free and has no irritant effect on the eyes. In addition no objectionable odors or tastes are produced.
In certain circumstances however which may vary greatly according to local conditions back-up treatment may be required to assist the algicidal activity of the polymeric biguanide. The problem exists however with this reagent that most of the currently available back-up agents are not compatible with this reagent and as a result chemical degradation occurs.